Introduction to safety in process plant

1. by
MOHD HAFIZ DZARFAN BIN OTHMAN
&
MOHD FADIL ABDUL WAHAB
Gas Engineering Department
Faculty of Petroleum and Renewable Energy Engineering
Universiti Teknologi Malaysia
n When you gamble with safety, you bet
your life
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Introduction to Chemical Process
Safety
Modern chemical plants use advanced and complex
technology.
Chemical plants are the safest of all manufacturing
facilities.
…….BUT …….
it has the potential for accident of CATASTROPIC
proportions.

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…….since we utilize advanced safety technology/tools
for the complex chemical processes……..
We need engineers with,
- sound technical knowledge (fundamental and
application) of process safety
- experiences
in order to effectively apply the technology.

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n “Safety” used to mean:
Strategy of accident prevention through
the use of safety helmet, safety shoes and
a variety of rules and regulation
– the emphasis was on workers safety
- Obeying safety rules
- Wearing PPE

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n Nowadays, “safety” is used synonymously with “loss
prevention”:
The emphasis is on:
The prevention of accidents through
-The use of appropriate technologies
-Identification of hazards of a chemical plant and
eliminate them before an accident occurs….i.e.
proactive….
n Safety also means freedom from unacceptable risk of
harm [see ISO/IEC Guide]

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Term Definition
Accident Undesired event giving rise to death,
ill health, injury, damage or other loss
Incident Event that gave rise to an accident or had potential
to lead to an accident (not all incidents propagate into
accidents)
(An incident where no ill health, injury, damage,
or other loss occurs is referred to as ‘near-miss’)
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Term Definition
Hazard Source or situation (chemical or physical) with a potential
to cause harm, injury or damage to either human, property
or the environment or some combination of these.
Mechanical hazards e.g. wet floor could cause tripping,
moving equipment that could cause collision etc.
Chemical hazards e.g. fuel leakage could cause fire,
explosion, toxic fumes form hazardous chemical etc.

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Term Definition
Risk Combination of the likelihood (probability) of a specified
hazardous event (e.g. accident) occurring and its
consequences
Risk
Assessment
The process of estimating the magnitude of risk and
deciding whether or not the risk is tolerable
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More definitions…
• Occupational safety – the protection
of people/workers from physical
injury
• Occupational health – the protection
of the bodies and minds of people/
workers from illness

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• To ensure safe design, installation, commission,
and operation throughout the life of a plant.
• Need to identify all potential hazards or incident
scenarios and to minimize all risks using loss
prevention techniques such as:
- inherent safety concept in design
- hazard identification methods
- technological advances using better design/
control
- proper maintenance etc.
Notes
Any potential hazards need to be identified as early as possible
so that action can be taken to correct or mitigate the situation.
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Safety Program
A successful safety program needs,
• System e.g. OSHMS: SHC, SHO, Policy, Regulation (Act) etc.
• Attitude or awareness
• Fundamentals (technical knowledge to design,
construct, operate, maintain etc.)
• Experience (learn from past accident and experience of others)
• Time (to train, to set up system, to do hazard identification,
risk assessment, documentation and review etc.)
• You….everyone should participate/contribute

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AICHE’s Code of Professional Ethics
Fundamental principles
• Engineers shall uphold and advance the integrity,
honor and dignity of engineering profession by :
1- using knowledge & skill for enhancement of
human welfare.
2- honest and impartial and serving with fidelity
to public, employers, clients.
3- striving to increase competence and prestige of
engineering profession.
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AICHE’s Code of Professional Ethics
Fundamental canons (for engineers)
• Shall hold paramount safety, health and welfare of public in
performance of their professional duties.
• Shall perform services only in areas of their competence.
• Shall issue public statements only in an objective and
truthful manner.
• Shall act in professional matters for each employer or client
as faithful agents or trustees, shall avoid conflicts of interest.
• Shall build their professional reputations on merits of their
services.
• Shall act in such manner as to uphold and enhance the
honor, integrity and dignity of engineering profession.
• Shall continue their professional development throughout
their careers and shall provide opportunities for professional
development of those engineers under their supervision.

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• Accident and loss statistics are used to measure
the effectiveness of safety programs.
• Among statistical methods used to characterize
accident and loss performance :
1. OSHA Incidence Rate
2. Fatal Accident Rate (FAR)
3. Fatality rate or deaths per person per year
• These methods report number of accidents and/or
fatalities for fixed number of workers during
specified period.
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The term OSHA refers to,
Occupational Safety and Health Administration, USA
….i.e. similar to Department of Occupational Safety and
Health (DOSH) in Malaysia
In Malaysia, the term OSHA 1994 stands for Occupational
Health and Safety Act 1994.

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Some glossary of terms used by OSHA (USA)
• Occupational injury- Any injury such as cut, fracture,
sprain, burn, amputation etc as a result from work accident
or from exposure involving single incident in the work
environment.
See Table 1-2 for more definitions
• Occupational illness- Any abnormal condition, caused by
exposure to environment factors associated with
employment. It includes acute and chronic illnesses or
diseases that may be caused by inhalation, absorption,
ingestion, or direct contact.
• Lost workdays- Days which employee normally work but
could not because of occupational injury or illness. This day
does not include the day of injury.
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1. OSHA Incidence Rate (OSHA IR)
• Based on cases per 100 worker years.
1 worker year =
50 work weeks
yr
40 hrs
week
= 2000 hrs
100 worker years = 100x2000 = 200,000 hrs worker exposure to hazard
• Two types of calculation
OSHA IR(1) : Based on injuries and illness (including fatalities)
OSHA IR(2) : Based on lost workdays

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OSHA Incidence Rate (OSHA IR)
OSHA IR(1) =
Number of injuries/illness/fatalities x 200000
Total hrs work by all employees during period covered
OSHA IR(2) =
Number of lost workdays x 200000
Total hrs work by all employees during period covered
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Examples,
1) A company with 100 workers recorded 10 injuries in one
year.
OSHA IR(1)=
10x200000
100x2000
= 10
We could say OSHA IR as a number of injury
per 200000 working hours or exposed hours

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Cont. Examples,
2) A company with 50 workers recorded 10 injuries in one year.
OSHA IR(1)=
10x200000
50x2000
= 20
Calculate OSHA Incident Rate for a company with 10 workers
recorded 10 injuries in one year?
Calculate OSHA Incident Rate for a company with 50 workers
recorded 10 injuries in 6 months?
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2. Fatal Accident Rates (FAR)
• FAR is used by British chemical industries. FAR data is widely
available in open literature.
• Based on 1000 employees working for 50 years during their
lifetime.
so, 1000x50x2000 = 108 working hrs or exposed hrs
We could say FAR as no of deaths per 108 working hrs or
108 exposed hrs.
FAR =
Number of fatalities x 108
Total working hrs by all employees during period covered

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For example:
In Table1-3, FAR for construction industry is 5.4 for year 2007,
This means that if 1000 workers begin employment in the
industry, 5 or 6 of the workers will die as a result of their
employment throughout all of their working lifetimes (i.e. 50
years).
Check:
FAR=
5.4x108
1000x50x2000
=
5.4x108
108
= 5.4
FAR = 5.4 =
Yx108
50000x2000
Y = 5.4 fatalities
or
We could say that for every 50000 workers in the construction
industry in year 2007, 5.4 of them died in work related accident.
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More rock climbers are killed traveling by car than are killed
during rock climbing. Is this statement supported by
statistics?
From data Table 1-4, Traveling by car, FAR=57,
Rock climbing, FAR = 4000.
Statistics say rock climbing produces more fatalities per
exposed hrs. …………BUT the climbers are actually spend
more time (exposed hrs) traveling by car.
We need more data (i.e. exposed hrs) to actually calculate the
number of fatalities.

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For example:
A rock climbing club has 1000 members working in chemical
industry, on average each member spend 3 hrs/day driving
and 2 hrs/month climbing. In 10 years how many member will
die due to rock climbing, road accident and occupational
accident.
FAR=
Number of fatalities x 108
Total working hrs by all employees during period covered
in this case,
FAR=
Number of fatalities x 108
Total exposed hrs by all members during 10 year period
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Answer:
ROCK CLIMBING
Number of fatalities =
FAR
108
x(Total hrs climbing by all member in 10 years)
Number of fatalities =
4000
108
x(1000x2x12x10) = 9.6 deaths
ROAD ACCIDENT
Number of fatalities =
FAR
108
x(Total hrs on the road by all member in 10 years)
Number of fatalities =
57
108
x(1000x3x365x10) = 6.2 deaths
OCCUPATIONAL ACCIDENT
Number of fatalities =
FAR
108
x(Total hrs working by all member in 10 years)
Number of fatalities =
1.2
108
x(1000x2000x10) = 0.24 deaths

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The OSHA Incidence Rate and FAR accident statistics,
in Table 1-3, showed a decrease for all selected industries
for 1990 as compare to 1978.
Discuss why?
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3. FATALITY RATE
Unit for Fatality Rate is deaths/person.year
Easy to use if the number of working hrs or exposed
hours is poorly defined.
FAR can be converted to Fatality Rate (or vice versa) if number of
exposed hours is known. See next example.
Fatality Rate =
Number of fatalities per year
Total number of people in applicable population

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Ex. 1-1
A process has a reported FAR of 2. If an employee works 8 hr shift 300
days per year, compute the deaths per person per year (or Fatality Rate).
Fatality Rate = Exposed hrs/person/year( )x(FAR)
Fatality Rate =
8hr
day.person
300day
yr
2deaths
108hr
= 4.8x10−5 deaths
person.year
OSHA incidence rate cannot be converted to FAR or Fatality Rate
because it contains both injury & fatality information.
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Exercise
An industry has a reported FAR of 57. If an employee works 8 hr shift 300
days per year, compute the deaths per person per year (or Fatality Rate).
Fatality Rate = ?

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Risk
Acceptance and
ALARP Concept
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• Risk cannot be eliminated entirely.
• Every chemical process has a certain amount of risk
associated with it.
• At some point in the design stage someone needs to
decide if the risks are “tolerable".
• One tolerability criteria in the UK is “As Low As
Reasonably Practicable" (ALARP) concept, formalized in
1974 by United Kingdom Health and Safety at Work Act.
• Tolerable risk is also defined as the risk that has been
reduced to a level that can be endured by the
organization having regards to its legal obligations and
its own OHS policy

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The Accident Pyramid
1 Death/Disabling injury
100 Minor Injury
500 Property Damage
10,000 No Damage (near misses)
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• Individual risk (IR) is the frequency at which a
given individual may be expected to sustain a given
level of harm from specified hazard.
• Occupational risk is a risk that may happen at the
work place. Usually given in term of FAR.
• Societal risk is frequencies with which specified
numbers of people in a given population sustain a
specified level of harm from specified hazards.

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This framework is represented as a three-tier system as
shown in figure. It consists of several elements :
(1) Intolerable level: Beyond the upper-bound on
individual (and possibly, societal) risk levels
(2) Tolerable (ALARP) region between (1) and (3), risk
is undertaken only if benefit is desired after considering
the cost on individual and societal risk reductions.
(3) Negligible risk (acceptable region): below the
lower-bound on individual (and possibly, societal) risk
levels. This level not to warrant regulatory concern.
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INTOLERABLE
LEVEL
(Risk cannot be
justified on any
ground)
THE ALARP
REGION
(Risk is undertaken
only if benefit is desired)
BROADLY
ACCEPTABLE
REGION
(No need for
detailed working
to demonstrate
ALARP)
TOLERABLE only if risk
reduction is impraticable
or if its cost is grossly
disproportionate to the
improvement gained
TOLERABLE if cost of
reduction would exceed
the improvement gained
NEGLIGIBLE RISK

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• From one survey, 28% say chemicals do more good
than harm, 29% say more harm than good, 38% say
same amount of good and harm.
• Some naturalists suggest eliminating chemical plant
hazards by “returning to nature” e.g. to eliminate
synthetic fibers production and use natural fibers
such as cotton….. but FAR for agriculture is
actually higher than for chemical industry.
See table 1-3
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Accidents have direct, indirect and root causes:
Ø Direct cause – attribute to equipment failure or
unsafe operating conditions
Ø Indirect cause – not as readily apparent and can
generally be tied to some human failure
Ø Root cause – result of poor management safety
policies, procedures or decisions
Note:
This causes do not include natural hazards such as
flood and windstorm etc.

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Type of
accident
Probability of
occurrence
Potential for
Fatalities
(consequence)
Potential for
economic loss
(consequence)
1) Fire High Low Intermediate
2) Explosion Intermediate Intermediate High
3) Toxic release Low High Low (equipment).
Other such as
cleanup, legal etc
can be high
Table 1-6 : Three Type of Chemical Plant Accidents
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Note: Except for natural hazards, all of these causes can be traced back to human error.
Figure 1-7 Causes of losses for largest hydrocarbon-chemical plant accidents. (Data from The
100 Largest Losses, 1972–2001.)"

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Figure 1-8 Hardware associated with the largest hydrocarbon-chemical plant accidents. (Data
from The 100 Largest Losses, 1972–2001.)"
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Note: OSHA legislation on Process Safety Mgmt of Highly
Hazardous Chemicals was introduced (in USA) in the year 1992
Figure 1-9 Loss distribution for the largest hydrocarbon-chemical plant accidents over a
30-year period. (Data from The 100 Largest Losses, 1972–2001.)#

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Steps
(Accident process or
sequence of accident))
Desired effect Procedure (to defeat the accident process)
Initiation
(the event that starts the
accident)
Diminish
(eliminate this step
if possible)
Grounding & bonding
Inerting
Explosion proof electrical
Guardrails
Maintenance procedure
Hot work permits
Human factor design
Process design
Awareness of dangerous properties of chemicals
Propagation
(the events that
maintain/expand the
accident)
Diminish
(stop propagation)
Emergency material transfer
Reduce inventories of flammable materials
Equipment spacing and layout
Nonflammable construction materials
Installation of check & emergency valves
Termination
(the events that stop the
accident)
Increase
(to terminate as
quickly as
possible)
Firefighting equipment and procedures
Relief systems
Sprinkler systems
Deluge system
Installation of check and emergency shutoff
valves
Table 1-7 Defeating the Accident Process
Introduction to
Risk Ranking

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Determination of Risk
Risk = Severity x Likelihood
•
Extent
of
Damage
•
Probability
of
Fatality
•
Based
on
design
and
modeling
equa9ons
•
Likelihood
of
failure
•
Historical
data
•
Based
on
design
and
historical
data
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Risk is expressed as Rating
n Rating is typically
– simple to use and understand
– Not require extensive knowledge to use
– Have consistent likelihood ranges that cover the full
spectrum of potential scenarios
n In applying risk assessment
– Clear guidance on applicability is provided
– Detailed descriptions of the consequences of concern for
each consequence range should be described
– Have clearly defined tolerable and intolerable risk levels
n Following risk assessment
– Scenarios that are at an intolerable risk level can be
mitigated to a tolerable risk level on the matrix
– Clear guidance on what action is necessary to mitigate
scenarios with intolerable risk levels are provided

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Example of Multiple Consequences for a
Consequence Range
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Example of Likelihood Ranges

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Example Risk Ranking Categories
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Likelihood ranges based on levels of
protection

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Typical Consequence Range Criteria
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Risk Matrix
Risk = Probability of occurrence x Consequence of occurrence

30. In Chemical Health Risk
Assessment (CHRA):
Risk Rating (RR) is calculated as,
RR = √(HR xER)
HR: Hazard Rating
ER: Exposure Rating
To be covered later…….. 59
Example of Major Disasters
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• Flixborough, England 1974
Failure of temporary bypass pipe connecting reactor 4
to reactor 6 (this occurred while the reactor 5 was
undergoing repair)
Resulting in the release of 30 tons of liquid cyclohexane
Forming vapor clouds that exploded, killing 28 people,
injured 36. It was on saturday.
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Figure 1-10 A failure of a temporary pipe section replacing reactor 5 caused the Flixborough
accident.#

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Bhopal, India 1984
Contaminated methyl isocynate (MIC) caused runaway
reaction, temperature rise….. as well as pressure.
Vapor released through pressure relief system but the
scrubber and flare systems failed to function. 25 tons
of MIC vapor released.
Toxic cloud spread nearby town poisoning/killing 2500
civilian, injured more than 20,000. No plant workers
were injured or killed.
No plant equipment was damaged. The owner was
Union Carbide.
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• Seveso, Italy 1976
Reactor out of control, produced excessive side product
of extremely toxic TCDD (dioxin).
2 kg of vapor TCDD released to atmosphere through
relief system and heavy rain washed into soil.
250 people suffered from chloracne (skin disease).

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The Way Forward
• Safety comes first !!!
• Two Important Elements
– Human Factor
We Need Good Safety Management Practice
– Safe Design
Need to Incorporate Inherently Safe Design
• This class will look at both issues and more!